High-speed actuator for valves

Abstract

A high-speed actuator moves a valve stopper to a selected position to control material flow. The actuator includes a rod carrying first and second axially spaced solenoid armatures attached to the stopper. First and second solenoid coil surround and are spaced from the rod to bias the first solenoid armature along with the rod and valve stopper. A linear variable differential transformer (LVDT) responsive to the position of the second armature determines the instantaneous position of the valve stopper. A valve position control circuit receives a valve position set point from a user's input, and a valve position feedback signal from the LVDT. The valve position control circuit includes first and second solenoid coil drive signals that urge the first armature and stopper to the valve position set point. A signal generator circuit vibrates the valve about a set point to enhance material discharge.

1. An apparatus for controlling the flow of material in a material handling apparatus comprised of a material container having a discharge opening, said apparatus comprising:
 a) discharge conduit extending from the discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said container through said discharge conduit, said valve including a valve stopper and a valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures, said rod having a connector end connected to said valve stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, said rod and first and second armatures each having cross-sectional areas that are in the range 10% to 50% of the cross-sectional area of said discharge conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coil surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) responsive to the position of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control means adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said means urging said valve stopper to the desired valve position set point. 
 
     
     
       2. The apparatus of  claim 1 , wherein said LVDT has primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils. 
     
     
       3. The apparatus of  claim 2 , wherein said LVDT primary coil is driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature due to said second armature's cross-sectional area being substantially less than the cross-sectional area of said discharge conduit. 
     
     
       4. The apparatus of  claim 1 , wherein said control means includes a signal summing means to produce a valve position error signal by summing said desired valve position signal together with said instantaneous valve position signal. 
     
     
       5. The apparatus of  claim 4 , wherein said control means includes a first signal translating means for translating said valve position error signal into a first pulse modulated signal having a pulse width that increases as said valve position error signal increases. 
     
     
       6. The apparatus of  claim 4 , wherein said control means includes a second signal translating means for translating said valve position error signal into a second pulse modulated signal having a pulse width that decreases as said valve position error signal increases. 
     
     
       7. The apparatus of  claim 5 , wherein said control means includes a first driver means for driving said first solenoid coil with electrical current, said first driver means being responsive to said first pulse width modulated signal. 
     
     
       8. The apparatus of  claim 6 , wherein said control means includes a second driver means for driving said second solenoid coil with electrical current, said second driver means being responsive to said second pulse width modulated signal. 
     
     
       9. The apparatus of  claim 4 , wherein said control means includes a proportional-integral-differential (PID) compensator for compensating said valve position error signal to minimize position error settling time. 
     
     
       10. The apparatus of  claim 1 , wherein said control means further includes a sinusoidal signal generator to generate a valve shaking signal. 
     
     
       11. An apparatus for controlling the flow of bulk material from a hopper having a discharge opening, said apparatus comprising:
 a) discharge conduit extending from the discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said hopper through said discharge conduit, said valve including a valve stopper and a valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures, said rod having a connector end connected to said value stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, said rod and first and second armatures each having cross-sectional areas that are in the range of 10% to 50% of the cross-sectional area of said discharge conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coil surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) responsive to the position of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control means adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said means including first and second solenoid drive signals to move said first armature and said stopper to the desired set point. 
 
     
     
       12. The apparatus of  claim 11 , wherein said LVDT has primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils. 
     
     
       13. The apparatus of  claim 12 , wherein said LVDT primary coil is driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature. 
     
     
       14. The apparatus of  claim 11 , wherein said control means includes a signal summing means to produce a valve position error signal by summing said desired valve position signal together with said instantaneous valve position signal, 
     
     
       15. The apparatus of  claim 14 , wherein said control means includes a first signal translating means for translating said valve position error signal into a first pulse modulated signal having a pulse width that increases as said valve position error signal increases. 
     
     
       16. The apparatus of  claim 14 , wherein said control means includes a second signal translating means for translating said valve position error signal into a second pulse modulated signal having a pulse width that decreases as said valve position error signal increases. 
     
     
       17. The apparatus of  claim 15 , wherein said control means includes a first driver means for driving said first solenoid coil with electrical current, said first driver means being responsive to said first pulse width modulated signal. 
     
     
       18. The apparatus of  claim 16 , wherein said control means includes a second driver means for driving said second solenoid coil with electrical current, said second driver means being responsive to said second pulse width modulated signal. 
     
     
       19. The apparatus of  claim 14 , wherein said control means includes a proportional-integral-differential (PID) compensator for compensating said valve position error signal to minimize position error settling time. 
     
     
       20. A bulk material dispensing apparatus comprising:
 a) hopper having a discharge opening and a discharge conduit having an inside diameter of a given cross-sectional area extending from said discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said hopper through said discharge conduit, said valve including a valve stopper and a valve seat, said discharge conduit extending from said valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures, said rod having a connector end connected to said valve stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, said rod and first and second armatures each having cross-sectional areas that are in the range of 10% to 50% of the cross-sectional area of said discharge conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coil surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) responsive to the position of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control circuit adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said circuit urging said valve stopper to the desired valve position set point. 
 
     
     
       21. The apparatus of  claim 20 , wherein said LVDT has primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils. 
     
     
       22. The apparatus of  claim 21 , wherein said LVDT primary coil is driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature. 
     
     
       23. The apparatus of  claim 20 , wherein said control mean includes signal summing means to produce a valve position error signal by summing said desired valve position signal together with said instantaneous valve position signal. 
     
     
       24. The apparatus of  claim 23 , wherein said control means includes a first signal translating means for translating said valve position error signal into a first pulse modulated signal having a pulse width that increases as said valve position error signal increases. 
     
     
       25. The apparatus of  claim 23 , wherein said control means includes a second signal translating means for translating said valve position error signal into a second pulse modulated signal having a pulse width that decreases as said valve position error signal increases. 
     
     
       26. The apparatus of  claim 24 , wherein said control means includes a first driver means for driving said first solenoid coil with electrical current, said first driver means being responsive to said first pulse width modulated signal. 
     
     
       27. The apparatus of  claim 25 , wherein said control means includes a second driver means for driving said second solenoid coil with electrical current, said second driver means being responsive to said second pulse width modulated signal. 
     
     
       28. The apparatus of  claim 23 , wherein said control means includes a proportional-integral-differential (PID) compensator for compensating said valve position error signal to minimize position error settling time. 
     
     
       29. The apparatus of  claim 20 , wherein said control means further includes a sinusoidal signal generator to generate a valve shaking signal. 
     
     
       30. The apparatus of  claim 29 , wherein the amplitude and frequency of said valve shaking signal is adjustable via said sinusoidal signal generator. 
     
     
       31. An apparatus for controlling the flow of material in a material handling apparatus comprised of a material container having a discharge opening, said apparatus comprising:
 a) a discharge conduit extending from the discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said container through said discharge conduit, said valve including a valve stopper and a valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures, said rod having a connector end connected to said valve stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coif surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) having primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils, said LVDT primary coil being driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature due to said second armature's cross-sectional area being substantially less than the cross-sectional area of said discharge conduit, said LVDT being responsive to the position of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control means adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said means urging said valve stopper to the desired valve position set point. 
 
     
     
       32. An apparatus for controlling the flow of bulk material from a hopper having a discharge opening, said apparatus comprising:
 a) a discharge conduit extending from the discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said hopper through said discharge conduit, said valve including a valve stopper and a valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures said rod having a connector end connected to said valve stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coil surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) having primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils, said LVDT primary coil being driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature due to said second armature's cross-sectional area being substantially less than the cross-sectional area of said discharge conduit, said LVDT being responsive to the position Of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control means adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said means including first and second solenoid drive signals to move said first armature and said stopper to the desired set point. 
 
     
     
       33. A bulk material dispensing apparatus comprising:
 a) a hopper having a discharge opening and a discharge conduit having an inside diameter of a given cross-sectional area extending from said discharge opening; 
 b) a valve having a fully open position and a fully closed position controlling the flow of material from said hopper through said discharge conduit, said valve including a valve stopper and a valve seat, said discharge conduit extending from said valve seat; 
 c) a non-magnetic rod carrying first and second axially spaced solenoid armatures, said rod having a connector end connected to said valve stopper and extending from said stopper within said discharge conduit, said rod and said armatures having cross-sectional areas less than the cross-sectional area of said conduit, whereby material can flow between said conduit and said armatures; 
 d) a first solenoid coil surrounding said conduit to bias said first solenoid armature toward said valve's open position; 
 e) a second solenoid axially spaced from said first solenoid, said second solenoid coil surrounding said conduit to bias said first armature toward said valve's closed position; 
 f) a linear variable differential transformer (LVDT) having primary and secondary coils positioned around said discharge conduit and axially spaced from said first and second solenoid coils, said LVDT primary coil being driven by a current amplifier that compensates for a loss of magnetic coupling with said second armature due to said second armature's cross-sectional area being substantially less than the cross-sectional area of said discharge conduit, said LVDT being responsive to the position of said second solenoid armature to provide an instantaneous valve position signal; and 
 g) a valve position control circuit adapted to receive a valve position feedback signal from the LVDT and a desired valve position set point signal, said circuit urging said valve stopper to the desired valve position set point.